George Bush yesterday lashed out at critics of the Iraq war, accusing them of hypocrisy and claiming that their "baseless attacks" were undermining US troops.

"While it's perfectly legitimate to criticise my decision or the conduct of the war, it is deeply irresponsible to rewrite the history of how that war began," President Bush told a largely military audience in Pennsylvania, in a speech to mark Veterans' Day.

He pointed out that many of his Democratic critics had voted to give him war powers in 2002, and had also accused Saddam Hussein of stockpiling weapons of mass destruction.

"The stakes in the global war on terror are too high and the national interest is too important for politicians to throw out false charges," Mr Bush said. American troops, the president went on, "deserve to know that their elected leaders who voted to send them to war continue to stand behind them".

Some senior Democrats who voted for war have since regretted their vote, saying they were misled by the administration's presentation of the evidence.

Senator Edward Kennedy, who opposed the war, said: "It's deeply regrettable that the president is using Veterans' Day as a campaign-like attempt to rebuild his own credibility by tearing down those who seek the truth about the clear manipulation of intelligence in the run-up to the Iraq war."

Mr Bush's bluntly worded speech reflects White House awareness that the WMD justification of the invasion remains an open wound in the administration's flank, draining its credibility and vitality.

After Democrats called for a fresh investigation into the alleged manipulation of intelligence in the build-up to war, and the indictment of a White House aide for perjury brought the issue back to centre stage, the president's popularity has plumbed new depths. The US death toll, now well past 2,000, has weakened him further.

A poll published by Fox News shows that only 36% of Americans still think Mr Bush is doing a good job, his lowest rating since taking office nearly five years ago.

The president's declining popularity is rapidly taking a toll on his political clout. His personal intervention on behalf of the Republican candidate in the Virginia gubernatorial election backfired on Tuesday, producing a surprising Democratic margin.

There are also signs that discipline in Republican party ranks is beginning to break down as its congressmen nervously prepare for re-election next year.

The party leadership in the House of Representatives had to call off a vital budget vote on Thursday evening when it became clear it would be defeated, even after concessions had been made to Republican moderates.